JP4428986B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a light amount detector that detects the light amount of a backlight in order to control the luminance of a liquid crystal display device.

2. Description of the Related Art Conventionally, in order to control the brightness of a backlight of a liquid crystal display device, a photodetector that detects light leaking through a reflection sheet provided on the back of a liquid crystal module with a sensor is known (for example, a patent) Reference 1).
JP-A-10-2222084

  However, in the photodetector shown in Patent Document 1, light leaking through the reflection sheet is detected, but the reflection sheet is originally intended to reflect light, and is transmitted through the reflection sheet. Since the amount of light transmitted is small, in order to detect this transmitted light, a highly accurate sensor and an amplifier with high accuracy and a large gain are required, and there is a problem that the manufacturing cost increases. Also, the higher the reflectivity of the reflective sheet, the more efficiently the light emitted from the light source can be used as a backlight. Therefore, the higher the reflectivity of the reflective sheet, the better, but the higher the reflectivity of the reflective sheet, the better the efficiency. Then, in proportion to this, the amount of transmitted light becomes small, and there is a problem that the detection accuracy of the sensor, the gain of the amplifier, etc. must be further improved.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a light amount detector for a liquid crystal display device in which an optical sensor can obtain a sufficient amount of light.

The present invention is a light amount detector that detects light emitted from a backlight of a liquid crystal display device, and includes an optical sensor that provides an exposed surface on a part of a side surface of a light guide plate and detects light leaking from the exposed surface. It is characterized by that.

The present invention is characterized in that an inclined surface that reflects light leaking from the exposed surface toward the back surface of the liquid crystal display device is provided, and the reflected light of the inclined surface is detected by the optical sensor.

The present invention is characterized in that the inclined surface has an inclination of 45 degrees or more with respect to a display surface of the liquid crystal display device.

The present invention is characterized in that the side surface is a side surface in a direction orthogonal to a direction in which direct light from the light source travels.

According to the present invention, the inclined surface that reflects light leaking from the exposed surface toward the back surface of the liquid crystal display device has an inclination of 45 degrees or more with respect to the display surface of the liquid crystal display device, and the light reflected by the inclined surface. Since a part of the reflected light can be returned to the light guide plate by detecting a part of the light with an optical sensor, an effect of suppressing luminance unevenness around the exposed surface can be obtained.

  Hereinafter, a light amount detector of a liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings. First, with reference to FIG. 2, FIG. 3, the positional relationship which attaches an optical sensor to a liquid crystal module is demonstrated. FIG. 2 is a plan view of the back side of the liquid crystal module 1. In the liquid crystal module 1 shown in FIG. 2, cold cathode ray tubes are arranged on the upper and lower side surfaces (upper and lower sides of FIG. 2) as a light source for illuminating the liquid crystal panel from the back, so that the entire display surface has uniform luminance. The light guide plate is provided. The light quantity detector is used for luminance adjustment when light emitted from the light guide plate is used as a backlight. In FIG. 2, the code | symbol 11 is a light detection part which detects the light which leaks from a light-guide plate. FIG. 3 shows an enlarged view of the light detection unit 11 shown in FIG. The light guide plate 3 receives light from the light source from the upper and lower side surfaces, and diffused light caused by scattering in the light guide plate 3 travels in the direction of the liquid crystal panel (in the depth direction perpendicular to the paper surface of FIG. 3). Will be illuminated from. On the other hand, the left and right side surfaces (side surfaces to which no light source is attached) 32 of the light guide plate 3 are shielded from light by the mold frame 9, but only the light detection unit 11 has a space between the mold frame 9 and the light guide plate 3. Since the side surface 31 of the light guide plate 3 is exposed only in this portion (this is referred to as an exposed surface), diffused light in the light guide plate 3 leaks to the outside of the light guide plate 3. Also, in the space between the mold frame 9 and the light guide plate 3, in order to reflect the light leaked from the exposed surface 31 to the back side of the liquid crystal module 1 (vertical front direction to the paper surface), it is integrally formed with the mold frame 9. An inclined surface 91 is provided.

  Next, the details of the configuration of the light detection unit 11 shown in FIG. 2 will be described with reference to FIG. FIG. 1 is a cross-sectional view of the light detection unit 11 shown in FIG. In FIG. 1, reference numeral 2 denotes a liquid crystal panel. Reference numeral 3 denotes a light guide plate that uniformly illuminates the entire display surface of the liquid crystal panel 2 by scattering light from a light source that passes through the inside. Reference numeral 4 denotes a reflecting plate provided on the back side of the liquid crystal module 1, which functions to reflect light traveling outward from the light guide plate 3 and return it to the inside of the light guide plate 3. Reference numeral 5 denotes an optical sensor for adjusting the luminance of the backlight, and detects light leaked from the light guide plate 3. The optical sensor 5 is housed in a sensor holder 8 fixed to the chassis 7 on the back side of the liquid crystal module 1. The light leaking from the light guide plate 3 is reflected by the inner surface 81 of the light collecting hole provided in the sensor holder 8 and guided to the light receiving surface of the optical sensor 5.

  Next, the optical path of light in the light guide plate 3 will be described. Light emitted from a light source (not shown) is scattered in the light guide plate 3. The diffused light traveling toward the liquid crystal panel 2 becomes a substantial light source of the backlight, and illuminates the liquid crystal panel 2 from the back surface. Further, the diffused light traveling in the back direction of the liquid crystal module 1 is reflected by the reflecting plate 4 and similarly travels in the direction of the liquid crystal panel 2 to illuminate the liquid crystal panel 2 from the back surface. On the other hand, the diffused light traveling in the direction of the side surface of the light guide plate 3 is reflected or absorbed by the mold frame 9 surrounding the light guide plate 3. However, diffused light is emitted from the exposed surface 31 of the light detection unit 11 to the outside of the light guide plate 3. The mold frame 9 of the light detection unit 11 has a space between the exposed surface 31 of the light guide plate 3 and an inclined surface 91. The slope 91 has an inclination of about 60 degrees with respect to the display surface of the liquid crystal panel 2 (α shown in FIG. 1), and the surface of the slope 91 is a diffuse reflection surface. The light emitted from the exposed surface 31 is reflected by the surface of the slope 91, a part of the reflected light is received by the optical sensor 5, and a part of the reflected light returns to the light guide plate 3. At this time, since the inclined surface 91 has an inclination of 45 degrees or more, the width of the space formed between the mold frame 9 and the exposed surface 31 of the light guide plate 3 can be reduced, and one of the reflected light can be reduced. Since it becomes possible to return a part to the light-guide plate 3, the brightness nonuniformity of the optical detection part 11 periphery can be suppressed.

The light received by the optical sensor 5 is converted into an electrical signal by a known method, and the luminance of the liquid crystal display device is controlled based on the electrical signal.
Further, when the mold frame 9 is molded using a resin having a low reflectance, a reflective sheet having a high light reflectance is attached only to the surface of the slope 91. On the other hand, in the case of the mold frame 9 using a resin having a high light reflectance, the resin surface may be used as a reflecting surface.
In FIG. 1, the height of the slope 91 is the same as the thickness of the light guide plate 3, and the entire thickness direction of the side surface of the light guide plate 3 is the exposed surface 31, but a part of the thickness direction (for example, the thickness) 1/2) may be the exposed surface. By doing in this way, when the angle of the slope is 60 degrees, the space between the mold frame 9 and the exposed surface 31 can be further reduced.

  Thus, by detecting the light leaking from the light guide plate 3 by the optical sensor 5, the light from the light guide plate 3 which is a substantial light source of the backlight is directly detected, so that a sufficient amount of light can be obtained. Thus, the accuracy of brightness adjustment can be improved without using a high-precision optical sensor or a high-gain amplifier. In addition, by reflecting the leaked light from the light guide plate 3 toward the back surface of the liquid crystal module 1, the space between the light guide plate 3 and the mold frame 9 can be reduced as much as possible, thereby suppressing uneven brightness on the display surface. be able to. In addition, since the angle of the inclined surface 91 is set to 45 degrees or more with respect to the display surface of the liquid crystal panel 2, a part of the reflected light on the inclined surface 91 can be returned to the light guide plate 3, and uneven brightness can be suppressed. Become. In addition, since the side surface on which the exposed surface 31 from which light leaks from the light guide plate 3 is provided is a side surface orthogonal to the direction in which the direct light from the light source travels, only the diffused light is incident on the light sensor without direct light from the light source entering the photosensor. Therefore, a state equivalent to the light emission state of the backlight can be detected, and the accuracy of light amount detection can be improved.

  Next, another embodiment will be described with reference to FIG. The liquid crystal module 1 shown in FIG. 4 is different from the liquid crystal module 1 shown in FIG. 1 in that a mold frame 9 ′ that is integrally formed with the mold frame 9 is not provided, and a slope is provided on the side surface of the light guide plate 3. This is a point defined as a surface 32. By doing so, diffused light due to scattering in the light guide plate 3 is emitted from the exposed surface 32, and since this light can be directly detected by the optical sensor 5, it is not necessary to provide the inclined surface 91, and the configuration of the light quantity detector Can be simple.

It is sectional drawing which shows the structure of one Embodiment of this invention. 2 is a plan view of the back side of the liquid crystal module 1. FIG. It is the enlarged view to which the photon detection part 11 shown in FIG. 2 was expanded. It is sectional drawing which shows the structure of other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal module 2 ... Liquid crystal panel 3 ... Light guide plate 31 ... Exposed surface 32 ... Exposed surface 4 ... Reflector plate 5 ... Optical sensor 6, 7 ... Chassis 8 ... Sensor holder 9 ... Mold frame 91 ... Slope (reflective surface)

Claims (2)

A liquid crystal display device comprising a backlight comprising a light source and a light guide plate, and an optical sensor for detecting light emitted from the backlight,
The light source is disposed on one side of the light guide plate;
An exposed surface is provided on a part of the other side surface in contact with the one side surface,
Providing a slope that reflects light leaking from the exposed surface toward the back surface of the liquid crystal display device;
The slope has an inclination of 45 degrees or more with respect to the display surface of the liquid crystal display device,
Liquid crystal display equipment, characterized by detecting a portion of the light reflected by the inclined surface by the optical sensor. 2. The liquid crystal display device according to claim 1, wherein the surface of the inclined surface is a diffuse reflection surface.

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